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The economic impact from the decreasing population mobility of China's mainland during the epidemic - Preprints.org
Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 21 December 2020                             doi:10.20944/preprints202012.0530.v1

          The economic impact from the decreasing population mobility of
          China’s mainland during the epidemic
          Yi Xiao 1, Jian Peng 2, Yuan Chen 1 and Zheming Yuan 1,*

                                      1 Hunan Engineering & Technology Research Centre for Agricultural Big Data Analysis & Decision-making,
                                        Hunan Agricultural University, Changsha, Hunan, 410128, China
                                      2 College of Information and Intelligence, Hunan Agricultural University, Changsha, Hunan, 410128, China

                                      * Correspondence: zhmyuan@sina.com;

                                      Abstract: The COVID-19 pandemic caused by SARS-CoV-2 poses a devastating threat to human
                                      society in terms of health, economy and lifestyle. Establishing accurate and real-time models to pre-
                                      dict and assess the impact of the epidemic on the economy is instructive. We have designed a new
                                      model to quantitatively assess the impact of the COVID-19 on the economy of China’s mainland.
                                      The nominal GDP in the Q1 of 2020 that we predicted for China’s mainland with the Baidu Migra-
                                      tion Data is RMB 20,785.7 billion, which is less by 3.59% than that in 2019. The estimated value is
                                      confirmed roughly by the official report released in April 17, 2020 (RMB 20,650 billion, 6.8% year-
                                      on-year declined). Strict control measures during the epidemic have greatly reduced China's eco-
                                      nomic activity and had a serious impact on the country's economy. Orderly promotion of popula-
                                      tion mobility plays a decisive role in economic recovery.

                                      Keywords: Economic impact; Population mobility data; Prediction; Assess; Covid-19

                                      JEL Classification:
                                      C15;C31;C51;C53;C55;C63;I18

                                      1. Introduction
                                            The COVID-19 hit Wuhan, China on December 29, 2019 and spread quickly across
                                      entire mainland [1]. As for April 12, 2020, 82052 were infected by the virus, and the deaths
                                      were 3339. The 31 provinces in China’s mainland raised their public health response level
                                      to the highest level (level-1) on January 29, 2020. To contain the spread of the epidemic,
                                      Chinese government has to adopt a series of large-scale public health interventions, such
                                      as inter- and intra-city travel restrictions, Staying Home Exercise, and Keeping Social Dis-
                                      tancing. These immediate and decisive measures have brought the epidemic under effec-
                                      tive control in early March [2,3], but have also significantly restricted the population mo-
                                      bility in China’s mainland [4]. According to the Baidu Migration Data, the inter-city trav-
                                      elers and the intra-city activity intensity in 346 cities in the Q1 of 2020 were 1.266 billion
                                      and 123218, which are less by 36.25% and 12.90% when compared to that in the same
                                      period of last year (1.985 billion and 141479) respectively (Fig.1).

                            Figure1. The population mobility in the Q1 of 2019 and 2020 in China's mainland
                                      Data source: Baidu Migration website

           © 2020 by the author(s). Distributed under a Creative Commons CC BY license.
The economic impact from the decreasing population mobility of China's mainland during the epidemic - Preprints.org
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               The population mobility, especially the inter-city and the inter-province travels, involving transportation, accom-
          modation, catering, business activities, sightseeing and shopping, has close associations with the regional economy [5-
          7]. The nationwide travel restriction has brought the entire service industry including transportation, catering, tourism,
          entertainment, and offline business, into a stagnation. The manufacturing supply chains have been hit heavily or even
          been partially broken. All of these have enormous negative impacts on the social and economic activities in the Q1 of
          2020 in China’s mainland. According to a recent report from the National Bureau of Statistics, some economic indicators
          in China dropped sharply in January and February of the year 2020 when compared to that in the same period of last
          year, such as the fixed asset investment(-24.5%), the total retail sales of consumer goods(-20.5%), the exports(-15.9%),
          the industrial added value(-13.5%), the service industry production index(-13%) and the profits of large-scale industrial
          enterprises(-38.3%).
               The Purchasing Manager Index (PMI) is an international macroeconomic monitoring index [8]. The mean PMI was
          45.9 in the Q1 of 2020 in China’s Mainland, which is less by 7.65% and 8.02% than that in the Q1 and the Q4 of 2019
          respectively. PMI is a leading indicator predicting GDP and usually has 3-6 months ahead [9], however, it is obviously
          invalid to predict the GDP for the Q1 of 2020 through the PMI of the Q3 or Q4 of 2019 when the epidemic heavily hit
          the economy. Economists, banks and institutions, etc. predicted at the early stage of the epidemic that the GDP growth
          rate of China in the Q1 of 2020 would decrease from 6% to 1.2% ~ 4.4%, for example 1.2% (China Economic Situation
          Report Website), 1.4%(Bloomberg), 2.5% (Goldman Sachs Asia), 2.8%(Standard Chartered) and 4.4%( Chinese Academy
          of Social Sciences). However, the predicted value dropped sharply to negative growth, -4.2% ~ -11%, when the epidemic
          has spread further to the world and seriously affected China's exports, for example, -4.2%(Standard Chartered), -
          5%(Morgan Stanley), -6% ~ -10%(Justin Lin), -6.48%(20 chief economists of China Business News), -9%(Goldman Sachs
          Asia) and -11%(Bloomberg). Evaluating the real impact of the epidemic on China's GDP in the Q1 of 2020 needs to
          develop a new quantitative predicting model. Based on the population mobility data from the Baidu Migration and the
          GDP data of 31 provinces in China’s mainland in the Q1 of 2019, we established a multiple regression model and pre-
          dicted the GDP of each province in the Q1 of 2020, and the real impact of the epidemic on the economy of China’s
          mainland was also assessed.

          2. Materials and Methods

          2.1 Data sources
               The GDP data and the population size in 2019 and 2020 of each province are from National Bureau of Statistics of
          China (http://www.stats.gov.cn/) and its affiliates. The population mobility data on inter-city and inter-province from
          January 1, 2020 to March 31, 2020 (including the same period data in 2019) in China’s mainland is from the Baidu Mi-
          gration (Baidu Inc., Beijing, China. http://qianxi.baidu.com), which is a largescale dataset based on an application that
          tracks the movements of mobile phone users and publishes the data in real time [10]. The Baidu platform represents the
          inter-city travel population of each city with the immigration and emigration indicators. The intensity of intra-city pop-
          ulation movements in each city is the ratio of the number of people travelling within a city to the number of residents
          in the city [4].

          2.2 Model design
               In the economic field, many methods, such as the Auto-regressive Integrated Moving Average Model and the Pur-
          chasing Managers' Index, are used for predicting and evaluating the GDP. These methods often rely on the parameters
          of a stationary time series and the results are lagging [11-13]. When certain major events causing large fluctuations in
          economic indicators occur, these forecasting methods will become unreliable. In response to the impact of the epidemic
          on the global economy, we estimated a model based on real-time population migration data to predict and evaluate the
          impact of the epidemic on the economy in time.

          2.3 Select parameters for the model
                At the level of province, we checked the relationship between the GDP in the Q1 of 2019 among the total emigration
          index of travelers leaving for other provinces, the total inter-city emigration index within the province, the population
          size; the determined coefficient were 0.7362, 0.7000 and 0.6981, respectively. The relationship between the population
          mobility index and the GDP is significantly stronger than that between the PMI and the GDP, respectively as: 0.44 [14],
          0.514 [15] and 0.75 [16], which shows that the population mobility index can be used to predict GDP in real-time. As for
          the population development index, there is a strong correlation between the previous economic inverse ranking of a
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          certain region and the subsequent economic development in the same period [17], so we further checked the inverse
          ranking of the provincial GDP, and the determined coefficient was 0.7743.
                The emigration index of travelers leaving from the ith province to other provinces on the jth day is denoted as PEIij
          (i=1,2,…,31; j=1,2,…,90 for 2019 and 1,2,…,91 for 2020). The emigration index of travelers leaving from the kth city of the
          ith province to other districts on the jth day is denoted as CEIkij (k=1,2,…,m; m is the total number of cities in the ith prov-
          ince). Ratiokij represents the percentage of the number of travelers leaving from the kth city of the ith province to other
          cities in the same province to the total number of travelers leaving from the kth city on the jth day. PEIij, CEIki and Ratiokij
          are all listed in the Baidu Migration.
                For each province, the total emigration index of travelers leaving from the ith province to other provinces from
          January and February in 2019 can be calculated by the equation (1):
                    59
           x1i   PEI ij ,( i  1, 2,...31)                                                                                              (1)
                    j 1

                 The total inter-city emigration index within the province from January and February in 2019 can be calculated by the equation
          (2):
                     59       m
           x2 i   CEI kij  Ratiokij ,( i  1,2,...27)                                                                                 (2)
                    j  1 k 1

             For each city, its x2r (r=28=“Beijing”, 29=“Chongqing”, 30=“Shanghai”, 31=“Tianjin”) can be represented with the
          mean x2i of 27 provinces and adjusted by the population:
                             27

                           x          2i
           x2 r     27
                            i 1
                                                x5 r ,(r  28="Beijing", 29  "Chongqing", 30  "Shanghai", 31  "Tianjin")              (3)
                    x
                     i 1
                                  5i
                                       / 27

              For each province, the total emigration index of travelers leaving from the ith province to other provinces in March
          2019 can be calculated by the equation (4):
                     90
           x3 i   PEI ij ,(i  1, 2,...31)                                                                                              (4)
                    j  60

                 The total inter-city emigration index within the same province in March 2019 can be calculated by the equation (5):
                     90       m
           x4i       CEI
                    j  60 k 1
                                              kij    Ratiokij , (i  1, 2,...27)                                                         (5)

          Similarly, x4r of each city can be calculated by the equation (6):

                             27

                           x          4i
           x4 r     27
                            i 1
                                               x5 r , (r  28, 29,30,31)                                                                 (6)
                    x
                     i 1
                                  5i   / 27

          x5: the population size of each province in 2019, represented with the population of 2018 end.
          X6: the inverse ranking of the provincial GDP in the Q1 of 2019, represented with the ranking of the same period in 2018.
          Y: the nominal GDP (RMB) of each province in the Q1 of 2019.
               The data of the Q1 of 2019 for each province are listed in Table 1.
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                               Table 1. The nominal GDP and the population mobility data of each province in the Q1 of 2019.
                    Province                   x1             x2           x3            x4          x5×104         x6         Y×109
                     Anhui                   530.5           718.1        196.8        258.6         6323.6         21         7065.7
                     Fujian                  251.4           429.8        78.1         153.6         3941.0         24         8145.3
                     Gansu                   127.4           238.2        54.0         106.9         2637.3          5         1736.5
                   Guangdong                 1061.6         2125.6        266.8        867.5        11346.0         31         23886.8
                    Guangxi                  314.7           588.3        100.8        194.0         4926.0         13         4225.3
                    Guizhou                  267.4           428.6        96.4         157.9         3600.0         10         3205.8
                    Hainan                    79.0           305.5        32.5         136.5          934.3          4         1300.3
                     Hebei                   644.6           430.6        323.5        225.6         7556.3         19         8164.4
                     Henan                   564.9          1033.9        220.7        476.6         9605.0         27         11639.1
                Heilongjiang                 130.8           280.9        50.7         114.4         3773.1          6         3184.6
                     Hubei                   369.6           723.4        125.1        280.3         5917.0         25         9110.1
                    Hunan                    418.6           824.2        127.7        277.1         6898.8         23         8335.0
              Inner Mongolia                 185.2           237.3        81.6         102.6         2534.0         11         3578.5
                      Jilin                  125.9           274.1        50.9         128.0         2704.1          7         2701.8
                    Jiangsu                  803.0           979.2        341.6        388.2         8050.7         30         22883.8
                    Jiangxi                  328.4           368.3        102.7        114.6         4647.6         16         5373.1
                    Liaoning                 193.1           442.0        82.3         205.0         4359.3         17         5486.2
                    Ningxia                   53.9           123.9        24.0          56.8          688.1          3          752.4
                    Qinghai                   34.6           61.4         15.3          32.6          603.2          2          557.1
                    Shaanxi                  257.0           564.3        103.6        239.3         3864.4         12         5450.3
                   Shandong                  430.2           914.8        199.8        427.2        10047.2         29         20177.4
                     Shanxi                  203.3           398.8        94.5         186.4         3718.3         18         3533.2
                    Sichuan                  485.3          1209.0        165.5        427.4         8341.0         26         9653.2
                     Tibet                    12.0           15.9          4.4           8.2          343.8          1          324.1
                    Xinjiang                  49.5           231.9        15.9         120.1         2486.8          8         2177.7
                    Yunnan                   194.1           573.5        71.2         221.0         4829.5         14         3849.7
                    Zhejiang                 703.4           551.3        221.9        214.9         5737.0         28         13084.1
                     Beijing                 594.8          1117.8        273.6        554.5         2154.2         20         7409.6
                   Chongqing                 329.2          1708.5        107.4        663.9         3101.8         15         5102.3
                    Shanghai                 510.8          1117.8        232.6        665.7         2423.8         22         8308.3
                    Tianjin                  219.7           869.3        104.4        418.7         1559.6          9         5198.6
          Data source: Baidu Migration website and National Bureau of Statistics of China website Notes:
          Notes:
          x1: The total emigration index of travelers leaving for other provinces from January to February in 2019.
          x2: The total inter-city emigration index within the same province from January to February in 2019.
          x3: The total emigration index of travelers leaving for other provinces in March, 2019.
          x4: The total inter-city emigration index within the same province in March,2019.
          x5: The population size of each province in 2019.
          x6: The inverse ranking of the provincial GDP in the Q1 of 2018
          Y: The nominal GDP of each province in the Q1 of 2018.
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          2.4 The construction of the regression equation
                 The epidemic in China’s mainlandhas been brought under effective control in early March of 2020. On March 18,
          zero newly confirmed case was first reported. At the beginning of March, all provinces except Hubei began to recover
          economic activities orderly, and the population mobility in March was significantly higher than that in February. The
          share of the GDP in March to the GDP in the Q1 is usually 40%. Taking January, February and March as a whole, the
          importance of March will be diluted and the predicted value will be decreased.              To avoid the disturbance of the "Spring
          Festival" when comparing the economic indexes among different years or months, the GDP of January and February
          has always been viewed as a whole by the National Bureau of statistics. According to Table 1, the GDP of January and
          February (Y1-2) and the GDP of March (Y3) of each province can be predicted by the follow regression models.
          Y1-2=0.6×Y= 6.3621×x1 + 0.02842×x2+0.3015×x5 +58.8302×x6 (n = 31, R2= 0.8304, P
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          Y': The predicted nominal GDP of each province in the Q1 of 2020
              Feeding the regression models with the corresponding population mobility data in the Q1 of 2020, we got the
          predicted GDPs of January and February (Y'1-2) and the predicted GDPs of March (Y'3) for each province in 2020. In the
          Q1 of 2020, the consumer price index (CPI) rose by 4.9% year-on-year (National Bureau of Statistics 2020), the predicted
          GDPs in the Q1 of 2020 for each province (Y') can be adjusted by the following formula, and are listed in Table 2.
          Y'= (Y'1-2+Y'3)×1.049       (n = 31, R2= 0.8907, P
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          x'2: The total inter-city emigration index within the same province from January to February in 2020.
          x'3: The total emigration index of travelers leaving foe other provinces in March, 2020.
          x'4: The total inter-city emigration index within the same province in March,2020.
          x'5: The population size of each province in 2020.
          x'6: The inverse ranking of the provincial GDP in the Q1 of 2019
          Y': The predicted nominal GDP of each province in the Q1 of 2019.
                                            We predict that the nominal GDP of China in the Q1 of 2020 is RMB 20,785.7 billion, which is less by 3.59% when
          compared to the same period of last year (RMB 21,560 billion). This result is confirmed roughly by the official report
          released on April 17, 2020 (RMB 20,650 billion).
                                            According to the GDP data of each province in the Q1 of 2020 published by the National Bureau of Statistics, we
          conducted a correlation analysis over the predicted results, and the analytical results are shown in Figure 3.

                                            20000
           provincal GDP,predicted values

                                                          R² = 0.8907
                                            15000

                                            10000

                                             5000

                                               0
                                                    0        5000         10000        15000        20000        25000
                                                                    provincal GDP,true values

                                            Figure 3. The true and the predicted GDPs of 31 provinces of China’s mainland in the Q1 of 2020

          3. Results
                We used the stepwise linear regression method to select relevant parameters from the Baidu Migration Data and
          established a regression equation to predict the nominal GDP of China’s mainland in the Q1 of 2020 is RMB 20,785.7
          billion, which is less by 3.59% than that in 2019. Validity of this predicted value is strongly supported by the official
          report released on April 17, 2020 (RMB 20,650 billion). The Population mobility data provides an important reference
          method and a view for evaluating the impact of the epidemic on other economies and the global as a whole, and also
          provides a new indicator for the real-time economic prediction when the epidemic ends.
                Due to the international flights data is unobtainable, the international population mobility is not considered in our
          research, which may be one reason for the higher predicted value of this paper. It is an interesting topic to predict the
          GDP by using the real-time population mobility data and the leading PMI indicator. Since the Baidu Migration has
          stopped disclosing its migration data for theQ2 of 2020 from May 8th, we do not forecast and assess the GDP of China’s
          mainland in the Q2 of 2020.

          4. Discussion
               Although the population mobility has increased significantly since March and the PMI has rebounded
          sharply, China’s economy in 2020 is still not optimistic because it will continue to suffer from the global epidemic,
          and the expected target of the annual growth rate is most likely less than 6%. According to the National Bureau
          of Statistics of China, China’s economy grew by 3.2% year-on-year in the Q2, which is still lower than expected.
          Some suggestions are provided here. 1) Continue to actively enlarge the domestic demand. For example, fully
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          playing the advantages of China's large-scale market, actively enlarging the residential consumption, reasonably
          increasing the public consumption, starting the consumption in physical stores, continuing to maintain the online
          consumption enthusiasm, and releasing the consumption demand being suppressed for the epidemic. 2) Reason-
          ably enlarge the effective investment scale. For example, accelerating the construction of 5G network, data center
          and other new infrastructure, focusing on the layout of digital economy, life and health, new materials, and other
          emerging strategic industries and future industries. 3) Precision foreign trade. For example, guiding foreign trade
          enterprises to adjust their production capacity and structure so as to meet the special global consumption demand
          during the pandemic, and be a better "world factory" to fight against the pandemic. 4) Continue to carry out the
          proactive fiscal policy and the moderately easy monetary policy, further reduce taxes, fees and interest rates.

          Supplementary Materials: Code and data are available on the following GitHub repository: https://github.com/Xiao-
          Yii/Migration-economic-data.
          Author Contributions: Data curation, Yi Xiao; Formal analysis, Yi Xiao and Yuan Chen; Resources, Yi Xiao; Software,
          Yuan Chen; Writing – original draft, Yi Xiao and Zheming Yuan; Writing – review & editing, Jian Peng.
          Funding: This research was funded by the Scientific Research Foundation of Education Office of Hunan Province, China
          (17A096).
          Acknowledgements: We thank Baidu for providing population mobility data.
          Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in study design, data collection
          and analysis, the decision to publish, or in preparation of the manuscript.

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